Control system



Aug. 19, 1941'.

A. F. KENYON CONTROL SYSTEM Filed July 25, 1939 .Paf

INVENToR /60/720 /1/ e/Zyo/r.

BY l lf VyTNESSES.. www

ATToR Patented Aug. 19, 1941 Westinghouse ElectricV & Manufacturing Qompany, East Pittsburgh, Pa., a corporation' of Pennsylvania ApplicationJuly 25, 1939,LSe rial`No. 286,338

` 4 claims. ,(01. so- 32) Myinventon relates, generally, to control sysn items, and, more particularly, to systems for con- "trolling `the tension on strip'm'aterial as it i-sbe- `ing passedthrough a rolling mill.

In the operation of steel strip rolling mills, it is ydesirable that back and Vfront tensions be applied to the strip` as [it enters and leaves `the Working rolls. -For best results in the rolling operation, the front and back tensions should be much -greater than can be applied through the unwindf ing and Winding reel-s. `It has `become the pracst ice,l therefore,A lto provide tensioning devices betweentheunwinding reel and the Working rolls and `between the working rolls and the Winding `reel which will. function to provide much higher fronthandback'tensionsat the working rolls than thevvincling and unwinding reel tensions. `One such tensioning device for providing iront tension on the strip as it leaves 'the roll stand has {beenjin the form of arpulling device comprising a pairofdriven'rolls over which a partial wrap of;` the]r -strip is-t-aken in passing from the roll stand to the Winding reel. These tvvo rolls provide the front tension on the strip while the winding tension isindependent of the front tension.

4 lilseretofore, vthe 1rplls of `such pulling devices have beengeared together and driven by a single motor. `This method of operation hasbeen found unsatisfactory `forthe reason that small -differencesin `the diameters of the rolls of the pulling device cause slippage and buckling of the strip mgthe rolls and sometimes cause one of the rolls tocarry vall of the pulling load.

`'.lfhe objects of my invention are to provide an `individual motor drive and control system thereyforor strip, pulling idevices which lshall function [to properly distribute the. pulling load between the rolls of the pulling-devices, which shall be `simple and efficient in operation .and whichshall `loeinexpensive tomanufacture` install, `operate and maintain. n f

These and other objectsand advantages ofthe vinvention will Vbeapparent from the following` deytggtilecldescription taken -in connection with the accompanying drawing in which theisingle figure is 1a diagrammatic view of asingle stand strip rollingmill embodying the principal features `of my invention.

glshe striplY Il, leaves the. Working roll stand l2, it passes-in apartial wrap, around each .of the .pair

.of the,- puiling` .device t |,4 are .drivenby .the motors 24respectivelyyto subject the? strip to v,ofrolls of apulling deviceM and iswoundtupon l,a,.reel lf.` The imperi and lower rolls Ill` and: v2() tension as it leaves the roll stand l2. The motors `*22 and 24 `are connected. in series circuit relation `andmotor 22` is made to apply a greater tension to the strip than-the motor-24 either bythe `proper adjustment of the relative excitationsof `the motors, or by making motor22 of a greater power rating than motor 24.`

The Working roll stand -I2 and the Winding reel llt `are driven by the motors 2liY and-28, respectively, and suitable controllers 30, P32, 34 andv35 are rprovided for separately and collectively controlling the motors and'the potenti-alofthe generatorr 38,4Which is 4the-source ofpovver Vfor the motors during -the inching operations andthe Ynormal running ofi-the mill.

Considering `thesysteln` more in detail, the polarity of `the' potential supplied" to the motors by `thetgenerator=38 Ais selectively determined `by the reversing switch `4l] which, upon thesfelective energization ofthe relays 42' and- 44, supplies the desired polarity of energizing potentialffor' the `i'leld Winding 46 of thegenerator` 38 :from the source of direct currentV power', represented nby `the conductors AA-B, over `the conductors 48 and 59. -i-'Ihe direction of rotation ofthe motors '22s. 24, `26 andZB can-thus be controlled bythe controlling of `the polarityofthe generator 38.

-The value of the outputpotential of the generator 38 may be controlled byfthe-ield rheostatj52 so that any'desired potential may be supplied to 4the motors `22,4 24, "26 andf,28`to loperate themill atanyrequired speed ffor inching, threadingor running cf the mill.

-The armature of the motor 26 maybe connected to the main power conductors fX-TYby the switch 54 through `a` circuitwhich extends from the conductor]X` through conductor" 56,` contact `elernv-,entj of theswitch 54, conductor 60. the

armature of the.frieten-26,.conductor` 62, contact elementJ 6,4 .andthe conductor` .(56l to the .ecnductorY. 1' f i t A similar circuit-.for 'energizing the armatures of the motors 22and. 24 v-inrseriesncircuit rela- -tion is controlletl-by the switchftl and extends .fromthe conductor Xfthroughthe conductorl,

contactelement 'l2 ofthe switch 68, conductor J4, the; armatureni the. motor 24, .conductor 16, lthe armature of the motor22, conductor 18, -con- `tact element .of .the switch- 68 and conductor A82 tothe conductorY. A resistor 84 may bacon-- netted in @hunting relation Awith the armatures of themotors 22 Vand 24 bya switch 86 through a `circuit which .extends-` `fromthe conductorl 514 -through .the conductortllpcontact element'lll of the switch 86, the resistor 84, conductor 82, contact element 94 of the switch 86 and the conductor 96 to the conductor 18. The resistor 64 may be apportioned as a shunting resistance for the armatures of the motors 22 and 24 by a conductor 98 extending between the conductor 16 which connects the armatures of the motors 22 and 24 and an adjustable tap 99 on the resistor 84.

A switch is provided to connect the armature of the motor 28 to the power conductors X-Y through a circuit which extends from the conductor X through the conductor |02, the contact element |04 of the switch |00, the armature of the motor 28, conductor |06, contact element |08 of switch |60 and conductor ||0 to the conductor Y.

The controller 30 is provided for controlling the polarity of the generator 38 and the energization of the armature of the motor 26 for threading the strip through the rolls of themill stand I2 or inching the rolls of the mill stand in a forward or reverse direction. To operate the motor 26 in the forward direction, the movable contact elements of the controller 30 are actuated to the left-hand position which causes the contact element H2 to complete an energizing circuit for the relay 42 of the reversing switch 40. This circuit extends from the conductor B through the conductor ||4, conductor ||6, Contact element ||2, conductor H8, the winding of the relay 42 and conductor 48 to the conductor A. At the same time, the contact element |20 of the controller 30 completes a circuit for the switch 54 which extends from the conductor A through the conductor |22, conductors |23 and |24, contact element |20, conductor |26, conductor |28, the winding of switch 54 and conductor ||4 to the conductor B. Thus, by operating the movable contact elements of the controller 30 to the left-hand position, the armature of the motor 26 is connected to the power conductors X-Y and the relay 42 energizes the eld winding 46 of the generator 38 with such a polarity as to cause the generator 38 to energize the conductors X-Y with a polarity which will cause the forward rotation of the motor 26. Upon actuation of the movable contact elements of the controller 30 to the right-hand position, the motor 26 will be energized with such a polarity as to cause it to rotate in the reverse direction. When the movable contact elements of the controller 30 are moved to the right-hand position, the contact element ||2 completes a circuit for the relay 44 of the reversing switch 40 which extends from the conductor A through the conductors |22 and |23, contact element ||2, conductor |30, the winding of the relay 44 and conductors |32 and 50 to the conductor B. The contact element |20 completes a circuit for the switch 54 which extends from the conductor A through the conductor |22, contact element |20, conductors |24, |26, and |28, the winding of the switch 54 and the conductor ||4 to the conductor B.

Control of the motors 22 and 24 for threading the strip through the pulling device |4 and for inching the pulling device is provided by the controller 34. When the controller 34 is actuated to the left-hand position, the contact element |36 thereof completes a circuit for the relay 42 which extends from the conductor B through theconductors |38 and |40, the contact element |36, conductors |42 and ||8, the winding of the relay 42 and the conductor 48 to the conductor A. The contact element |44 of the controller 34 completes a circuit for the switch 68 which extends from the conductor A through the conductor |46, contact element |44, conductor 46, the winding of switch 68 and conductor |38 to the conductor B. The contact element |50 of this controller completes a circuit for the switch 86 which extends from the conductor B through conductors |52 and |54, contact element |50, co-nductors |56 and |53, the Winding of the switch 86, and the conductor |60 to the con-ductor A. The polarity of the generator 38 will thus be such as to provide forward rotation of the motors 22 and 24 .and the resistor 84 will be connected in shunting relation with the armatures of these motors to divide the voltage between the armatures to insure rotation of the motors 22 and 24. This shunting resistor 84 or some similar device is necessary during the threading or inching operations when there is not good contact between the strip |4 and the tensioning rolls I8 and 20 to assure rotation of both motors. During such time as these rolls are not tied together by the firm contact of the strip i4 with each of them, the motor having the least load may start and come up to speed, taking all the voltage of the series circuit and preventing the other motor from starting. With the resistor 84 connected in shunting relation with the armatures of the motors 22 and 24 and the parts of the resistor divided between the motors by the conductor 98 and the tap 99, the potential supply across the conductors X-Y will be divided between the motors 22 and 24 in accordance with the relative resistance of the parts of the resistor 84 on each side of the tap 90. Thus the resistor 84 may be proportioned between the motors 22 and 24 to insure that both will always start during the threading and inching operations.

Upon actuation of the controller 34 to the right-hand position, the contact element |36 will complete a circuit for the relay 44 of the reversing switch 40 which extends from the conductor A through the conductors |60 and |62, contact element |36, conductors |64, |30, the winding of relay 44 and the conductors |32 and 50 to the conductor B. Simultaneously, the con.. tact element |44 will complete a circuit for the switch 68 which extends from the conductor A through the conductors |46 and |66, contact element |44, conductors |68 and |48, the winding of switch 68 and conductor |38 to the conductor B. The contact element |50 will complete a circuit for the switch 86 which extends from the conductor B to the conductor |52, contact element |50, conductor |58, the winding of switch 86, and conductor |60 to the conductor A. Thus reverse rotation of the motors 22 and 24 for inching purposes is provided.

The controller 36 may be actuated to control the forward and reverse rotation of the reel motor 28. The actuation of the controller 36 to the left-hand position will cause the contact element |10 to close an energizing circuit for the relay 42 which extends from the conductor B through the conductors |12 and |14, contact element |10, conductors |16 and I8, the winding of relay 42 and the conductor 48 to the conductor A.

The contact element |18 will complete a circuit for the switch |00 which extends from the conductor A through the conductors |80, |82, and |84, contact element 18, conductors |86, |88 and |90, the winding of switch |00 and conductor |12 to the conductor B. Energization 'Lof fthe :reel motor 28am- '.the reverse directionis providedsby actuatingthe rcontro'ller36 .ltofthe 'fright-handtzpositionv toifcause 'thelcontact .ele- Wmenti H10 toescomplete an energizingicircuit for the relay 44 of the reversing switch 40 which extends from the conductor` :A through the con- AMductor |80, contact. element |10, conductors |92 -.and"`|30,itlie windingzof `relay44 and conductors .I32iand50 totheconductor- B. The Contact :element H0 .l meanwhile completesfa circuit for C Mthezswitch `IIl0 which. extends from Athe conductor .'LAL through conductors I88fand` 1.32, contact ele- 'rment` Ii'I.8,. conductorsizl88 `and |90, `the winding tof lrelay |500 and conductor II2 to the conductor B. vInfthreadingtthe strip I.0 `through Vthe mill and performing inching` operations, `the `output potenl tial of thengenerator 138 :may -be made much `lower than :the Knormal running potential` so that vfthe'tnotors -22,24,-26"and 28 .will Arun at a much lower'speed l l l. l

` iWlhen thestripfll hasvzbeen threadedthrough the-:roll: stand 1Iz2rand the pullingxdevice` I4 and Hstar-ted` on the `reel` 16; the drivemotors. fonthe :roll standlI:2,1-the..pullingxdevice "I4 and the reel :MIB mayfbevcontrolledsimultaneously to run in .the forward .directionaby .the controller 32; The :actuation of lthe controller` 32 .to `.the .left-.hand uposition Iwillenergize-the lrelay =.42- of -the re- "veising sw-itchfflt through a circuit which extends wire-mthevcoiiductorrB lthrough the conductor 1I-"56; contacte element A 194;` `conductors I 98 and "`I`-"I B, ""the winding `of Athe relay 42- and thecon- "ductor 481to-thefconductorlA. At the same time, the Contact element '206: 'will close an energizing circuit `for 'the swtch' 5.4 tot-:energize the `armature i l'o'ffthe rnotor26 which extends from theconductor J200, conductor `I28`,"the winding of the switch i54jand conductorjIIli `to the conductor B. The feo'itact" element 2,04`willcl`ose an energizing crcuit 'fo-rthe switchto.connectthevmotors 22 Hand' 124 inseries4 circuit relation `to be energized by'the generator `33 in al circuit which extends Ifrom the conductor A'throughthe conductors A.202- .and- 205, contact element 7204 conductors 250g, L60 and the winding of lswitch .B8-and the.conductorV -I38l to the conductor B. 'I'he ,ar-inature.fof the ,reel -motor 28 will also be enerlgized.'bythe energiz'ation .of its control switch I-00fftt1rougha:circuit whichis completed by the `Contact element 2Jmand-which-extends `from the fconiductonAthrough:the conductors202 and 2 I2, contact .element 5.2 |50, conductor.. I 90, the winding Mbyithe .tensioning-roll .LI 8 driven by .the 1 motor`22,

J-ithe` .tension applied to `ltheistrip l vby ltheztensioning rollt 2.@ Jdrivenubyfthe fmotor 24 and *the winding l-.tension Iti will hbeapparent therefore,- -that 4the 5 Lpressurefof-the lstrip'on the tensioning roll I8 will #bef greater `than -onthe tensioning roll 20. The rollfl will,-therefore, l'havefa greater traction 4fonthe stripi--thanthe 'tensioning roll 2ll'and jitwillbe possible to yapply amuch greater tension-to the strip through 'the tensioning roll-I8 "thaniithroughtithe tensioning. roll 253. 'In order 'to operate "thetensioning device most eiiciently, therj'e'fore,` a 'gre'ateramount of'thetension should -`'be supplied' bythe motor 22 throughzthe ten- @sioning rollj'l' than by the motor 24 through the `,tensioning1roll"`2 0 f In order to A,provide 4this `greater power output 24 provided with smaller excitation Athan `the' `motor 22". Thus, assuming that the power potential across. the conductors` Xu-.Y is 600volts and n the motors 22 and24 are 400 volt motors, if` the `.motor 24 is `excited at half its normal excitation, ..it-.wi;ll1be running. as` a 200 volt machine, motor .22Y willberunning as a 400^volt machineand-the `.motor 2.2 willbe .carrying twice asmuch load as the motorw24. p

A moreveicient method of operation1would wbeftorchoose. the relative sizes `of .the .tensioning '.rollidrive motors approximately. proportional .Lto `,the :loads toibo. .carried .by them, .as determined lbylthe .traction lof. the strip I0 upon their asso- J.ciated tensioning rolls. Thus, `if itis desired .thatthe `motor `22 carryl-three-fourths `oi the tensioning load and the? motor 24 carry only one Jfourthof-"the tensioningdoad, `the motors 22 and r24mayfbernade ofsubstantially the same cur- "rentfrating but of a voltage-rating-in the proportion oi--three tofone. Thu`s,`if themotorl 22 is a 450i volt-motor andthe' motor v24 is a 150 volt motor, since they have the'same armature current,jbeing connected in series circuitfthe .total `tensioning power will be divided'between ,them `inthe proportion of 450 l.to V150, orthree to one.

VIf; now, with motors 22 and`24 having substantiallythe same current ratings and voltage ratings 'in the proportion of three to oneinstalled on a particular mill, it is desired to provide a different proportioningof the load between the motors, `their excitations may be varied by 5 means. yoi the `rheostats indicated in circuit with of switch |00 and conductor H2 toconductor B. 5

.fThuslthe armatures of the motors 22, 24, 26 and 28 will be connected tothe power conductors X-Y to be energized by the generator 38, the generator 38 will be excited with such a polarity as toprovide energizing power for the motors 22, 24, 26 and 28 which will cause them to rotate in the forward direction, and the rheostat 52 may be manipulated to increase the output potential of the generator 38 and thus increase the speed of the motors to bring the mill up to normal running speed.

The strip I0 will be wound upon the reel I6 under a light tension, the amount of the winding tension being controlled by any suitable means which will control the torque of the motor'28. The front tension applied to the strip I0 as it leaves the roll stand I2, will be much greater than the winding tension and it will be equal to the sum of the tension applied to the strip 'their iield windings to vary the potentialdistribu'tion and, therefore, the power distribution between them.

In such a strip rolling mill as is described 60 herein, it is common practice to also provide a pulling device on the feeding side of the mill stand I2 between the roll stand I2 and an unwinding reel to provide back tension on the strip I0 as it enters the roll stand I2. Such pulling devices are similar to the pulling device I4 with braking generators driven by the tensioning rolls to provide a braking effect, and, therefore, a back tension on the strip I0, and the unwinding reel is also made to drive a braking generator to provide unwinding reel tension and to maintain back tension on the pulling device. It is to be understood that the invention herein described may be applied to such a mill to provide the most efficient operation of the pulling device 75 which provides back tension on the strip and that the control system described in detail herein may be extended and applied to the braking generators which are connected to the back pulling device and the unwinding reel by operating the reel I6 as an unwinding reel and operating the motors 22, 24 and 28 as braking generators to provide back tension as the strip I passes from the reel I8 to the roll stand I2. It is to be further understood that such pulling or tensioning devices as those described herein may be used to provide both front and back tension on a strip as it is passed through a rolling mill in the manner described in the Hudson Patent No. 2,054,819, and that the pulling device may be operated in either direction by causing the motors connected to the tensioning rollers to act as either motors or generators depending upon the direction of travel of the strip, as fully eX- plained in the copending application of G. P. Lessmann et al. Serial No. 210,194, filed May 26, 1938, now Patent No. 2,195,009, issued March 26, 1940.

The provision of the resistor 84 to be connected in shunting relation with the armatures of the motors 22 and 24 to insure rotation of the motors 22 and 24 during threading and inching operations is merely a convenient electrical system for performing this function and other means for performing this function may be provided, As an example, the motors 22 and 24 may be mechanically connected together by a light friction belt so that if there is a tendency of one to rotate 'and the other to stand still due to unequal distribution of load between them, they will both be made to rotate by the mechanical connection. Such a connection would be only a friction connection in which there may be some slippage to permit slight differences of speeds of rotation of the motors due to slight diierences in the diameters of the tensioning rolls to which they are connected. Such a mechanical connection may also be provided connecting the tensioning rolls I8 and 20 instead of the motors 22 and 24.

It will be apparent that I have provided a tension control system for a strip rolling mill which shall function to properly distribute the pulling load between the rolls of the pulling devices of the mill which shall be simple and efficient in operation and which shall, be inexpensive to manufacture, install and repair.

In compliance with the requirements of the patent statutes, I have shown and described herein the preferred embodiments of my invention. It is to be understood, however, that the invention is not limited to the precise constructions shown and described but is capable of modication by one skilled in the art, the embodiments herein shown and described being merely illustrative of the principles of my invention.

I claim as my invention:

l. In a strip tension control system, in combination, a pair of spaced rolls over which the strip passes in frictional engagement, a drive motor for each of the said rolls, circuit means energizing the armatures of said motors in series circuit relation, and means for Varying the relative values of the excitations of said motors whereby one of said motors will subject the strip to a greater tension through its associated roll than the other motor, voltage dividing means for providing a predetermined energization of each of the armatures of said motors, and means for rendering said voltage dividing means eiective.

2. In a strip tension control system, in combination, a pair of spaced rolls over which a strip which is being acted upon by a work device passes in frictional engagement, a dynamoelectric machine mechanically connected With each of said rolls, circuit means connecting the armatures of said dynamo-electric machines in series circuit relation, means for varying the relative values of the excitations of said dynamoelectric machines to thereby cause diierent tension forces to be transmitted between the strip and the two dynamo-electric machines through their associated rolls, and means for ensuring rotation of both of the rolls during inching operations of the work device.

3. In a strip tension control system for a strip rolling mill, in combination, a pair of spaced rolls over which the strip passes in frctional engagement, a motor connected in driving relation with each of the rolls, circuit means connecting the armatures of said motors in series circuit relationpvoltage dividing means for providing a predetermined energization of each of the armatures of said motors, Iand means for rendering sald voltage dividing means eective during the inching operations of the mill.

4. In a strip tension control system for a strip rolling mill, in combination, a pair of spaced rolls over which the strip passes in frictional engagement, a motor connected in driving relation with each of the rolls7 circuit means connecting the armatures of said motors in series circuit rela.- tion, and means for ensuring rotation of both of the rolls during the inching operations of the mill, when the strip is not in frictional engagement with both of the rolls.

ALONZO F. KENYON. 

